JP2014188912A - Mold and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove an once generated weld line by reflowing the same without being influenced on the number of gates.SOLUTION: The mold comprises: a plurality of movable mold pars of forming a part of molding face in a molding; and a control part making at least one movable mold part among a plurality of the movable mold parts movable toward the inside of the molding, and making at least one movable mold part among a plurality of the movable mold parts movable toward the outside of the molding.

Description

  The present invention relates to a mold and an injection molding method.

  In the injection molding, when a split flow of the resin filled by the core or the like provided in the cavity occurs, a weld line is generated at a portion where the split resin flows are merged and integrated.

  Various techniques related to such a background are known (see, for example, Patent Document 1).

  For example, Patent Document 1 describes an injection molding method for remarkably improving the strength around a weld line of a molded product that originally produces a weld line and can obtain only a very low weld line strength. More specifically, in this injection molding method, in the injection molding of the thermoplastic resin, the flow of the flow dividing resin flow path from the point where the molten resin to be injected and filled flows to the weld line formed by the merge of the flow divided resin. Using a mold that has a resin reservoir with a piston that can be advanced and retracted on at least one side, protruding from the molded product cavity, and supplying the molten resin to the mold with the piston retracted or advanced, the weld After the line is formed, the piston is advanced toward the molded product cavity and the resin filled in the resin reservoir is pushed into the cavity, or the piston is retracted and the weld line is drawn into the resin reservoir from the cavity. The resin on the one side that presses the weld line is pressed into the resin on the other side. To strengthen the emissions. In this way, depending on the injection molding method, the resulting molded product can reinforce the weld line very efficiently by disturbing the orientation of the resin or filler in the weld line.

  Further, when the molten resin is injected from the injection molding machine into the cavity in the mold, a so-called weld line appears as a hair-like line at a portion where two or more molten resin flows merge.

  Various techniques relating to such a background are known (see, for example, Patent Document 2).

  For example, Patent Document 2 describes an injection molding method for a plastic product, for example, a resin rod used for a suspension rod for automobiles or a resin cylinder member of a cylindrical vibration-proof rubber. More specifically, this plastic product injection molding method injects a material sent from an injection molding machine and fills the cavity with the material. In the injection molding method of the plastic product, after the material is injected into the cavity, the material from the injection molding machine is sent out of the cavity and the driving means is operated by the pressure of the material. And this plastic product injection molding method is the piston means which alternately repeats the material in the cavity by the operation of the drive means, but the material is advanced from both sides of the weld line, compressed and retracted to release the compression. Is activated. Thus, depending on the injection molding method of the plastic product, it is not necessary to provide a separate drive unit, and the material for molding the plastic product can be used as a drive source as it is, and the device itself can be provided at low cost.

  In addition, when a resin case having at least one of a hole, a recess, and an insert member is molded using a mold, a forming pin or an insert member for forming a hole, a recess, or the like is previously formed inside the mold. After being set at a predetermined position inside the mold, the molten resin is injected and filled into the mold.

  Various techniques related to such a background are known (see, for example, Patent Document 3).

  For example, Patent Document 3 describes a resin case manufacturing method in which a resin case having at least one of a hole, a recess, and an insert member is molded using a mold. More specifically, this resin case manufacturing method fills a mold with a molten resin. Then, this resin case manufacturing method is characterized in that at least one of a forming pin and an insert member for forming a hole and / or a recess is injected into a mold and immediately before completion of resin filling in the mold. Push into the molten resin in the mold. Thus, depending on the method of manufacturing the resin case, even if the resin case is formed with at least one of a hole, a recess, and an insert member, there is no residual weld line inside and the resin case can ensure the resin strength. Can be provided.

  In injection molding using a synthetic resin as a molding material, various molding defects may occur depending on molding conditions and the shape of the resin molded product.

  Various techniques related to such a background are known (see, for example, Patent Document 4).

  For example, Patent Document 4 describes a temperature control method for a resin molding die that forms a molding cavity for molding a resin molded product made of a synthetic resin with a molten synthetic resin. More specifically, in the method for controlling the temperature of the resin molding die, the resin molding die is provided with a nest for forming a molding cavity. In this method for controlling the temperature of the resin molding die, one or two or more medium passages for passing a temperature control medium only through the insert are provided. And this temperature control method of the resin molding die insulates between the insert and the resin mold except the insert. The temperature control method for the resin molding die indirectly measures the temperature in the cavity, and interrupts the flow of the low-temperature cooling medium through the medium passage when the temperature in the molding cavity falls below a predetermined lower limit temperature. Then, a high-temperature heating medium is caused to flow through the medium passage. In this resin molding mold temperature control method, when the temperature in the cavity exceeds a predetermined upper limit temperature, the flow of the high-temperature heating medium is interrupted and the low-temperature cooling medium is allowed to flow in the medium path. In the temperature control method for the resin molding die, a high-temperature heating medium and a low-temperature cooling medium are alternately passed through the medium passage. In this way, depending on the temperature control method of the resin molding die, a medium path for passing the temperature control medium is provided only in the nest that is insulated from the surroundings, and a high-temperature heating medium flows through the medium path. Since only the insert is heated and a low-temperature cooling medium is flowed through the medium passage to cool only the insert, the heat energy is used very efficiently, and the inside of the molding cavity is rapidly heated and cooled. be able to.

Japanese Patent No. 2960256 JP 2000-836 A JP 2009-78519 A JP 2011-178149 A

  Depending on the technique described in Patent Document 1, it is difficult to control the piston forward and backward, assuming the resin filling state from the sensor and weld formation time, and the piston is advanced and retracted after filling the resin. In this case, the resin in the cavity becomes excessive or insufficient.

  In the technique described in Patent Document 2, a material flow path is separately provided as a drive source for the piston means. Therefore, depending on the technique described in Patent Document 2, every time the molded product is taken out, the material in the flow path must be discarded, and the material is wasted. Further, the technique described in Patent Document 2 has a complicated structure and is difficult to realize.

  Further, in the technique of Patent Document 3, the pin is pushed in immediately before the resin in the mold is completely filled, but it is difficult to drive the pin in accordance with the flow of the resin in the mold cavity in actual control. It is. If the timing of driving the pins does not match, there is a risk that a weld line will eventually occur or that resin will remain between the mold cavities on the side where the pins abut and the pins will cause molding defects such as burrs.

  Further, in the technique of Patent Document 4, since the flow path of the molten resin is not changed, in a colored resin in which a filler or the like is contained in the resin, a single flow portion and a portion where two or more flows are merged Then, since the direction of the filler in the resin changes, it becomes conspicuous on the appearance like a weld line.

  The objective of this invention is providing the metal mold | die and injection molding method which solve the subject mentioned above.

  In order to solve the above-described problem, according to the first aspect of the present invention, there are provided a plurality of movable mold parts that form a molding surface of a part of a molded product, and a plurality of movable mold parts. Among these, at least one movable mold part is moved toward the inside of the molded product, and at least one movable mold part among the plurality of movable mold parts is moved toward the outside of the molded product. With.

  According to the second aspect of the present invention, in the injection molding method, at least one movable mold part among a plurality of movable mold part movable mold parts forming a part of the molding surface of the molded product, While moving toward the inside of the molded product, at least one movable mold portion among the plurality of movable mold portions is moved toward the outside of the molded product.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. Also, a sub-combination of these feature groups can also be an invention.

  As is apparent from the above description, according to the present invention, the weld line once generated can be removed by reflowing.

It is a figure which shows an example of the injection molding method using the metal mold | die which concerns on 1st Embodiment. It is a figure which shows the flow which reduces the flow of the molten resin generate | occur | produced with the cavity shape of the metal mold | die of FIG. 1, a weld line, and a weld line. It is a figure which shows the example which provided multiple sets of space which stores molten resin, and made the reflow of the molten resin after filling more efficient. It is a figure which shows the example which reflows molten resin using a part of cavity of a metal mold | die.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all combinations of features described in the embodiments are described below. However, this is not always essential for the solution of the invention.

  FIG. 1 shows an example of an injection molding method using a mold according to the first embodiment. When the cavity 1 of the mold according to the present embodiment is formed into a shape that is actually necessary, a hole 2 is opened at the center thereof, and it can be said that a weld line WL is easily formed by the flow 8 of the molten resin after injection molding.

  The metal mold | die which concerns on this embodiment is equipped with the storage spaces 4 and 6 of the same volume which can store molten resin on the extended line of the cavity 1 on the outer side of the cavity 1. FIG. Further, the mold has driving mechanisms 5 and 7 for extruding the molten resin stored in the storage spaces 4 and 6 into the cavity 1 and storing the molten resin in the cavity 1 on the back surface thereof. ing. The storage space 4 may be an example of the “first movable mold part” in the present invention. The storage space 6 may be an example of the “second movable mold part” in the present invention.

  At the time of injection molding, the storage spaces 4 and 6 are moved by the drive mechanisms 5 and 7 so that one of the storage spaces 4 and 6 is opened (a state in which molten resin can be stored) to increase the volume of the cavity 1, and the other is closed (the cavity 1 is closed). And is operated to reduce the volume of the cavity 1. Each drive mechanism 5, 7 performs an opening / closing operation in conjunction with each other.

  The storage spaces do not necessarily have to be paired, and it is sufficient that the storage spaces have the same volume when opened and closed.

  2 shows the flow 104 of the molten resin 102 generated in the cavity shape of the mold 101, the weld line WL, and the flow for reducing the weld line WL (FIGS. 2C to 2D). Here, in addition to a general injection molding resin, an example of a molding resin in which a filler 103 is kneaded in a resin is shown.

  (From FIG. 1A) The molten resin storage space 6 on the side close to the gate 3 is closed at a position following the line of the cavity 1 by the drive mechanism 7 and the storage space 4 far from the other gate 3 is driven. Open by mechanism 5.

  (From FIG. 1 (B)) The flow of the molten resin injected into the cavity 1 from the gate 3 is divided into two at one surface of the central hole 2 and merges at the opposite surface. A weld line WL is generated at this merge. The molten resin is then filled into the storage space 4. The portion where the weld line WL is generated is also shown in FIGS.

  When the cavity 1 and the storage space 4 are filled with the molten resin (from FIG. 1C), the drive mechanisms 5 and 7 work together to close and store the storage space 4 to a position that follows the line of the cavity 1. By opening the space 6 so that the molten resin can be stored, the molten resin in the cavity 1 becomes a flow 8 different from that in FIG. 1B, and the weld line WL once generated is pushed away and removed. When filler or the like is kneaded in the molten resin as shown in FIG. 2, since the directions of the fillers of the front and back surfaces of the cavity 1 and the weld line WL are different, a particularly clear weld line WL appears. By reflowing the molten resin once filled as in 2 (C) → (D), the direction of the filler can be made uniform.

  Here, if the fluidity of the portion in contact with the mold is improved by increasing the temperature of the mold, which is a known technique for preventing the weld line WL, further improvement of the weld line WL is expected.

  Furthermore, it is considered that the effect of removing the weld line WL is improved by repeating the opening and closing operations of the storage spaces 4 and 6 a plurality of times.

  As described above, according to the injection molding method using the mold according to this embodiment, the first effect can be removed by reflowing the weld line WL once generated.

  In addition, the direction of the filler can be made uniform by reflowing to a kneaded resin such as a filler, which is effective for injection molding that requires appearance.

  Another embodiment will be described with reference to FIGS. Although the basic configuration and operation are the same as those shown above, FIG. 3 shows an example in which a plurality of storage spaces for storing the molten resin are provided, and the reflow of the molten resin after filling is made more efficient. is there. After the storage mechanisms 4 and 6 are closed / opened by the drive mechanisms 5 and 7, the storage spaces 10 and 12 are closed and opened by the drive mechanisms 11 and 13, so that the molten resin can be reflowed in a larger range. . FIG. 4 shows an example in which the molten resin is reflowed using a part of the cavity 1 (molded product shape). If the cavity 1 has a portion corresponding to the same volume as the storage space 6, the drive mechanism can be provided without worrying about the parting line generated on the mating surface of the mold.

  The closing / opening operation does not necessarily have to be performed for each pair of combinations, and it is only necessary to be able to control the same volume or pressure for closing and opening.

  Part or all of the above embodiment can be described as in the following supplementary notes, but is not limited thereto.

  (Appendix 1) A plurality of movable mold parts forming a part of the molding surface of the molded product, and at least one movable mold part among the plurality of movable mold parts is directed toward the inside of the molded product. A mold comprising: a control unit configured to move and move at least one movable mold part of the plurality of movable mold parts toward the outside of the molded product.

  (Additional remark 2) The said control part controls the movable position of the said movable mold part by the movable area | region of the said movable mold part, The metal mold | die of Additional remark 1 characterized by the above-mentioned.

  (Additional remark 3) The said control part controls the movable position of the said movable mold part with the pressure of the said movable mold part, The metal mold | die of Additional remark 1 characterized by the above-mentioned.

  (Supplementary Note 4) Any one of Supplementary Notes 1 to 3, wherein the control unit moves at least one movable mold part among the movable mold parts toward the inside and the outside of the molded product. The mold according to one item.

  (Supplementary Note 5) At least one of the movable mold parts is disposed on a start end side of the resin injection part, and at least one of the movable mold parts is disposed on a terminal side of the resin injection part. 5. The mold according to any one of appendices 1 to 4, wherein

  (Appendix 6) The mold according to any one of appendices 1 to 5, wherein the shape of the movable mold part also serves as a part of the shape constituting the molded product.

  (Appendix 7) Among a plurality of movable mold parts that form a part of the molding surface of the molded product, at least one movable mold part is moved toward the inside of the molded product, and An injection molding method comprising: moving at least one movable mold part among a plurality of movable mold parts toward the outside of the molded product.

  (Additional remark 8) The injection molding method of Additional remark 7 characterized by flowing the resin with which the cavity of the metal mold | die was made to flow by moving the said movable metal mold | die part repeatedly.

  (Supplementary note 9) The injection molding method according to supplementary note 7 or 8, wherein the movable mold part is moved after the cavity of the mold is filled with resin.

  (Additional remark 10) The movable area | region when moving the said movable mold part toward the inside of the said molded object, and the movable area | region when moving the said movable mold part toward the outer side of the said molded object become equal. The injection molding method according to any one of appendices 7 to 9, wherein the movable mold part is controlled as described above.

  (Additional remark 11) The pressure at the time of moving the said movable mold part toward the inside of the said molded object and the pressure at the time of moving the said movable mold part toward the outer side of the said molded object become equal. The injection molding method according to any one of appendices 7 to 9, wherein the movable mold part is controlled.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Cavity 2 Hole 3 Gate 4 Storage space 5 Drive mechanism 6 Storage space 7 Drive mechanism 8 Flow 10 Storage space 11 Drive mechanism 12 Storage space 13 Drive mechanism 101 Mold 102 Molten resin 103 Filler 104 Flow WL Weld line

Claims (10)

A plurality of movable mold parts forming a molding surface of a part of the molded product;
Among the plurality of movable mold parts, at least one movable mold part is moved toward the inside of the molded product, and among the plurality of movable mold parts, at least one movable mold part is And a control unit that is movable toward the outside of the molded product. The said control part controls the movable position of the said movable mold part by the movable area | region of the said movable mold part. The metal mold | die of Claim 1 characterized by the above-mentioned. The said control part controls the movable position of the said movable mold part with the pressure of the said movable mold part. The metal mold | die of Claim 1 characterized by the above-mentioned. The said control part moves at least 1 movable mold part among the said movable mold parts toward the inside and the exterior of the said molded object. The mold described. At least one of the movable mold parts is disposed on the start end side of the resin injection part,
5. The mold according to claim 1, wherein at least one of the movable mold parts is disposed on a terminal end side of the resin injection part. The mold according to any one of claims 1 to 5, wherein a shape of the movable mold part also serves as a part of a shape constituting the molded product. Among a plurality of movable mold parts forming a molding surface of a part of the molded product, at least one movable mold part is moved toward the inside of the molded product, and the plurality of movable molds An injection molding method characterized by moving at least one movable mold part of the mold part toward the outside of the molded product. The injection molding method according to claim 7, wherein the resin filled in the mold cavity is caused to flow by repeatedly moving the movable mold part. The injection molding method according to claim 7 or 8, wherein the movable mold part is moved after the cavity of the mold is filled with resin. The movable region when moving the movable mold part toward the inside of the molded product and the movable region when moving the movable mold part toward the outside of the molded product are equal to each other. The injection mold method according to any one of claims 7 to 9, wherein the movable mold part is controlled.

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